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  • 1995-1999  (8)
  • 1980-1984  (15)
  • 1
    Electronic Resource
    Electronic Resource
    Spin Fluctuations in the Normal State Optical Conductivity (1999)
    Springer
    Journal of superconductivity 12 (1999), S. 667-673 
    Details
    ISSN: 1572-9605
    Keywords: A.C. conductivity ; spin fluctuations ; oxides ; spectral density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A theory is given for the structure present in the normal state optical conductivity that reflects the underlying spin fluctuations for a system in which the charge carriers interact through the antiferromagnetic spin susceptibility. Such an interaction involves strong momentum anisotropies and energy dependence that modulates the frequency dependence of the conductivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007756220115
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  • 2
    Electronic Resource
    Electronic Resource
    Coupling strength of charge carriers to spin fluctuations in high-temperature superconductors (1999)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 401 (1999), S. 354-356 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In conventional superconductors, the most direct evidence of the mechanism responsible for superconductivity comes from tunnelling experiments, which provide a clear picture of the underlying electron–phonon interactions. As the coherence length in conventional superconductors is large, ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/43843
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  • 3
    Electronic Resource
    Electronic Resource
    Optical Conductivity in Orthorhombic d-Wave Superconductors (1999)
    Springer
    Journal of low temperature physics 115 (1999), S. 251-280 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The large anisotropies observed in the in-plane transport properties of untwinned single crystals of YBa 2 Cu 3 O 6.95 reside in the orthorhombic nature of its band structure which includes CuO chains as well as CuO 2 planes. An infinite band model with distinct effective mass in a and b-direction is used to study the a.c. conductivity of a d-wave BCS superconductor. A subdominant s-wave admixture is also included in the gap because both symmetries belong to the same irreducible representation in an orthorhombic system. Parameters are fit to experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021879520432
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  • 4
    Electronic Resource
    Electronic Resource
    On the critical temperature of anisotropic superconductors (1982)
    Springer
    Journal of low temperature physics 47 (1982), S. 157-167 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An approximate analytic formula for the increase in the superconducting critical temperature caused by anisotropy is derived and compared with both the results of exact numerical solutions of the Eliashberg equations and with a previous approximate formula due to Allen and Butler. In all the cases considered our new formula is found to be more accurate than the previous one and to agree reasonably well with the exact results for the intermediate and weak coupling superconductors considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00682025
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  • 5
    Electronic Resource
    Electronic Resource
    On the effective spectral densities for a superconductor with paramagnons (1984)
    Springer
    Journal of low temperature physics 57 (1984), S. 291-305 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Solutions of generalized Eliashberg equations containing an explicit paramagnon contribution are generated and used to obtain tunneling characteristics, which are then inverted in order to recover an effective spectral density. We consider several shapes for the paramagnon spectral density and vary the characteristic paramagnon energy. We invert the information on the gap using both the generalized and conventional Eliashberg equations and compare the effective spectral functions obtained by these methods with each other and with the actual kernels for the electron paramagnon and electron phonon spectral density. Scaling laws relating approximately the inverted and actual kernels are established and limitations on these laws described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00681194
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  • 6
    Electronic Resource
    Electronic Resource
    Thermodynamics of superconducting lanthanum (1983)
    Springer
    Journal of low temperature physics 51 (1983), S. 135-148 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have calculated the thermodynamics of superconducting lanthanum from numerical solutions of the finite-temperature Eliashberg equations, written on the imaginary frequency axis, with electron-phonon kernel taken from the available tunneling data. We compare the theory with a recent specific heat determination of the thermodynamics. Also, we study several possible changes in the spectral density chosen to improve agreement with experiment. Our favored spectrum is obtained by a constant scaling of the tunneling spectral density chosen to increase the mass enhancement parameter from 0.79 to approximately 1.0.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683418
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  • 7
    Electronic Resource
    Electronic Resource
    Detailed study of the thermodynamics of a superconductor with paramagnons (1981)
    Springer
    Journal of low temperature physics 42 (1981), S. 585-600 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: The effect of paramagnons on the thermodynamics of a superconductor has been studied within Eliashberg theory. For model microscopic parameters approximating those characteristic of Nb we compare results for finite and zero paramagnon mass enhancement parameter, λspin. The change obtained in the thermodynamics is significant, but because of present uncertainties in the experimental data and in the value of the calculated electron-phonon interaction, an accurate value of λspin cannot be determined. The effect of spin fluctuations on the quasiparticle density of states in the region of phonon energies is also investigated. Our results have implications for tunneling inversion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00117432
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  • 8
    Electronic Resource
    Electronic Resource
    A comparative study of the thermodynamics of superconducting Nb0.75Zr0.25 and Nb (1981)
    Springer
    Journal of low temperature physics 43 (1981), S. 131-138 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: From the microscopic parameters derived from tunneling for Nb0.75Zr0.25 and Nb we compute and compare their thermodynamic properties using the imaginary frequency axis formulation of Eliashberg theory. While these two materials have similar critical temperatures, Nb0.75Zr0.25 is found to show much larger strong coupling corrections than does Nb. The substantial increase in the gap to critical temperature ratio observed experimentally can easily be understood by functional derivative techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00118626
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of normal impurities on anisotropic superconductors with variable density of states (1982)
    Springer
    Journal of low temperature physics 47 (1982), S. 411-426 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We develop a generalized BCS theory of impure superconductors with an anisotropic electron-electron interaction represented by the factorizable model introduced by Markowitz and Kadanoff, and a variable electronic density of statesN(ε), assumed to peak at the Fermi energy, which is modeled by a Lorentzian superimposed on a uniform background. As the impurity scattering is increased, the enhancement ofT c by both the anisotropy and the peak inN(ε) is washed out. The reduction is investigated for different values of the anisotropy and different peak heights and widths. It is concluded that the effects of anisotropy and the peak are reduced together in such a way that any effect due to anisotropy is not easily distinguishable from that due to the peak.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683982
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  • 10
    Electronic Resource
    Electronic Resource
    Impure anisotropic superconductors with variable density of states peaked away from the Fermi energy (1983)
    Springer
    Journal of low temperature physics 50 (1983), S. 113-122 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A generalized BCS-type theory of impure superconductors with an anisotropic electron-electron interaction and variable electronic density of states is extended to the case in which the Fermi energy εF falls at an arbitrary position within the peak. It is found that when εF is well away from the center of the peak, then the reduction in the transition temperature due to the washing out of the anisotropy can in some cases be distinguished from that due to the density of states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00681842
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